coolant channel can be stopped during reactor operation, allowing for online refueling. RBMK fuel enriched to 2 percent typically reaches an average burnup of about 30,000 megawatt days per metric ton of heavy metal (MWd/MTHM).1

The VVER reactors operate with UO2 fuel enriched to 3.0– 4.4 percent,2 sealed in zirconium alloy rods. The VVER rods are roughly half the length of RBMK assemblies. The rods are removed during refueling outages, one to two years apart (depending on fuel enrichment). VVER fuel typically reaches an average burnup of approximately 50,000 MWd/MTHM in a VVER-440 and 40,000–45,000 MWd/MTHM in a VVER-1000. The other two types of reactors are the liquid metal fast reactors (BN series), only one of which, the BN-600, now operates as a commercial power reactor, (the BOR-60 operates as a pilot power station), and the Bilibino boiling water graphite reactors (EGP-6 reactors), which are small versions of the RBMK reactors. The BN-600 at the Beloyarsk nuclear power station is cooled with sodium and has steelclad UO2 fuel, enriched to 17–33 percent.

Six VVER-440 reactors (pressurized water reactors) operate in Russia and generate 87 MTHM of SNF annually. After discharge from the reactors, the SNF is stored in cooling pools for a period of 3–5 years, and then it is shipped in casks to the reprocessing plant, RT-1, at PA “Mayak.” The cooling pools at the reactor sites are typically filled only to 20–25 percent of their capacity. If shipments of the SNF offsite were to halt, however, the pools would be filled in four to five years. Breached SNF assemblies (now numbering 60) from VVER-440 reactors are stored in separate sections of the cooling pools. These assemblies are expected to be shipped to the RT-1 plant for reprocessing by 2007.

Another 21 VVER-440 reactors operate in European countries outside of Russia. Shipments of VVER-440 SNF from these countries to Russia have diminished in recent years. As noted earlier, Russia intends to take back the SNF from those reactors, and is currently storing and reprocessing SNF from at least some of them for a fee. Seven VVER-1000 reactors operate in Russia and generate 190 MTHM of SNF annually. Another 17 VVER-1000

1  

The theoretical maximum burnup for fuel of this composition—that is, the energy released if every nucleus of uranium were fissioned—is approximately 940,000 MWd/MTHM.

2  

Enrichment is 3.6 percent on average for VVER-440s and either 3.3 or 4.4 percent for VVER-1000, depending upon the length of the operating cycle (Rosenergoatom 2002).



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